21 
a 
THURSDAY, MARCH 21sr, 1907. 
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Common Parasites of Cat and Dog. 
BY 
MetGatt. LIVESE ¥) MRC V.s., 
Illustrated by Specimen Lantern Slides. 
ARASITES. What is a parasite? Not merely one animal 
living upon another. Because a fox lives upon rabbits and 
poultry he is not therefore a parasite! One animal is only said 
to be a parasite upon another when the size of the consumer is 
small or even inconsiderable when compared with that of its victim. 
As a rule, animals of a lower order are more often parasitic upon 
those of a higher order, and not the higher upon the lower. 
But every small animal found upon a larger one is not 
necessarily a true parasite. Thus there is mutualism where two 
animals may live together and benefit result to both; commensalism 
where only one finds benefit, but no injury results to the host 
which acts as a harbour of refuge or supplies most favourable 
conditions of existence ; true parasitism where again only one of 
the two benefits, but it benefits to the extent of shelter and 
sustenance at the expense and to the detriment of its host. 
Parasitism is very common throughout the natural world, 
and we see it on all sides, and the study of parasitology is 
elucidating many facts concerning disease. I feed only mention 
the comparatively new science of bacteriology to remind you 
how science has developed during the last few years, and proved 
that many conditions, which we call disease both in man and 
animals, do not arise, as had been believed for scores of years, 
from purely physical causes but from the presence of minute 
vegetable organisms, bacteria or more commonly called microbes. 
Also let me remind you how such diseases as malaria, supposed 
at one time to be due to bad climate, is now proved to be due to 
minute animal parasites in the blood, having been inoculated 
into the system by the bite of the mosquito. 
I am not going to speak of these minute parasites to-night, 
but will confine my attention to those which hold higher places 
in the natural orders, and of course I only want to draw your 
attention to a few of those parasites which are commonly to be 
found upon dogs and cats in this country. The number is very 
large for these animals, and the dog especially makes an excellent 
host and pays dearly for the privilege. By this statement I 
